PROJECT SUMMARY - INTERACTION OF PHYTOHORMONE SIGNALING PATHWAYS Candidate: The candidate's long-term career goal is to become a principal investigator in an academic setting, studying the interaction networks involved in phytohormone response. During the training period, she will learn biochemical research approaches to complement her graduate applied agricultural and post- doctoral molecular genetic research. Training Environment: Rice University provides an ideal training environment because of its quality research and intimate setting. Dr. Bonnie Bartel, the mentor for this project, is a leader in Arabidopsis research. Further, she is an active mentor who devotes the majority of her time to her research and her postdocs and students. Research: The long-term goal of this project is to enhance understanding of the signaling network that connects the phytohormones auxin, abscisic acid (ABA), and ethylene. The dual-specificity protein phosphatase, IBR5, the subject of this proposal, is a novel point of interaction between auxin, ABA, and ethylene signal transduction networks. Several interconnected approaches will use IBR5 to gain greater understanding of the relationship among these phytohormones. Firstly, IBR5-interacting proteins will be identified (Aim 1); these may include substrates and regulators of the IBR5 phosphatase. Additionally, second-site ibr5 modifiers will be analyzed (Aim 2) to determine whether sensitivity to auxin, ABA, and ethylene can be separated, or if they are interconnected in inseparable ways. Identification of defective genes in these modifiers (Aim 3) will allow molecular elucidation of interactions between these phytohormone pathways. These studies will contribute to understanding of which signaling components are shared among these three pathways and which are not shared, and will identify additional nodes in the phytohormone signaling network. In addition to expanding our basic knowledge, a detailed understanding of these three phytohormones, involved in growth responses, stress tolerance, and fruit ripening, may provide insight for the eventual improvement of plants of agricultural or medicinal importance. For instance, determining how to increase stress tolerance (ABA perception) without altering growth characteristics (auxin perception) or ripening (ethylene perception) could be key to adapting plants to high stress areas (i.e., areas of low rainfall or saline soils).